Troubleshooting

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Returning a Starter to Sky-Tec
After you've completed the troubleshooting process and determined the starter needs servicing, click here to obtain a Return Authorization number online.

Basic Troubleshooting

PRINTABLE VERSION

IMPORTANT NOTES: THIS DIAGRAM REPRESENTS ONLY ONE POSSIBLE STARTER WIRING SCENARIO. THERE ARE OTHERS. DO NOT USE THIS DIAGRAM AS GUIDANCE FOR INSTALLING YOUR STARTER! Installation information is ALWAYS included with each starter and can also be found on the product specific pages of this website (listed in blue blocks above left).

Also,

DO NOT REMOVE THE STARTER FROM THE AIRCRAFT TO PERFORM TESTING! For accuracy and relevance, starter testing should be conducted in the aircraft while the starter is in its failure mode. Please do NOT use jumper cables to test starters - it will not provide useful information. Use an analog voltmeter if at all possible. An ohmmeter will not provide useful information - keep it simple & follow these easy steps:

Pretest Considerations: If possible, visually inspect the starter and/or interview pilot/operators for starting history. Indications of long cranking periods, burning odor or smoke from the starter, kickback(s), a cracked starter mount, a fast spinning starter w/no prop movement (for Sky-Tec NL model starters replace shear pin), oil in starter, grinding noise or a damaged ring gear are generally indications that the starter is in need of repair and the following tests will not be helpful. Remove the starter for repair or overhaul (the NL model starter shear pin is FIELD REPLACEABLE - do not return to Sky-Tec for shear pin repair).

Testing Relevance: The following testing procedure is most relevant to Lycoming starters and some Continental starters that are low performing including slow cranking and/or failure to crank the engine over a compression stroke. If a starter is damaged by overcranking or a stuck firewall solenoid, voltage in step one may read below acceptable levels thus incorrectly indicating a potential battery problem. Therefore, in such cases some consideration must be to the pretest conditions noted above (if it smells burned...). If the only effect of energizing the starter results only in an audible “click” with no prop movement, confirm step 2 to isolate problem to starter or starter contactor. For Sky-Tec CvST3 (Continental) model starters: Sky-Tec CvST3 starters feature an inspection port. If starter rotates but prop does not, remove inspection plug and note clutch drum rotatation. If rotation is observed, starter is OK - suspect starter adaptor.

	*TEST*	*RECORD*	*RESULT*	*ANALYSIS*
	Record voltage at the battery while cranking the starter in its failure mode.	______ *VOLTS*	Below 10.0* volts? Above 10.0* volts? - Proceed to Step 2	Questionable battery. See Testing Relevance above as a shorted (cooked) starter will pull voltage down appreciably. However, if starter rotates at all, this is generally not a shorted starter condition.
	Record voltage at the starter while cranking the starter in its failure mode.	______ *VOLTS*	No voltage recorded Above 9.0* volts? Below 9.0* volts and: - Difference between Step 1 and Step 2 exceeds 2.0* volts - Difference between Step 1 and Step 2 less than 2.0* volts	Starter OK. Test Starter Solenoid or switch (Step 3) Suspect Starter. Suspect Cables, terminals and/or solenoids - proceed to Steps 3 & 4 Borderline Condition (old Piper?)- Call factory with test results to discuss. If happens more when cold, suspect battery. When hot, suspect cables/terms/sols.
OPTIONAL
	Record voltages between each and every cable terminal and across solenoids while cranking the starter in its failure mode.		Assuming the voltage difference noted in Step 2 exceeded 2.0* volts, flush out any appreciable loss in voltage in any cable or solenoid by placing the meter along each link in the diagram. A tight electrical system will lose no more than 0.5 volts between the battery and starter. Be sure to conduct these tests while cranking the starter in its failure mode.
	Record voltages between battery & ground and starter & ground while cranking the starter in its failure mode.		If no appreciable loss of voltage is noted in Step 3, flush out the integrity of all electrical system grounds. Pay close attention to battery and engine grounds. Clean up or repair any questionable ground connections and re-test.

Troubleshooting Talk
Common Complaints and Credible Culprits

	Application	Complaint	Question	Culprit
The Bump & Run	All - Lyc/Cont/Franklin	When starter engages, the prop moves (some distance), and then stalls on the first compression stroke. After repeated attempts, starting is successful (usually).	Does it happen any more (or less) when the engine is hot?	Voltage. Rarely a starter issue. Most starters do not have a "weak" state. They either work great or not at all. Typically, this slowing of the cranking is a sign of a loss of voltage. If it happens when hot, suspect bad cables or solenoids. If it happens when cold (or always), suspect a bad battery. But the Troubleshooting Guide can help isolate the voltage loss.
The Bump & Grind	Lycoming	When starter engages, it makes a terrible "grinding" noise.	Has the engine ever had a kickback when cranking?	A spark before Top-Dead-Center while cranking will break starters (and other accessories as well). In the case of old, heavyweight starters, kickbacks broke teeth off the ring gear. Sky-Tec LS/PM & HT starters (excl. HTI starters) are designed to break when an engine fires before top-dead-center during cranking. In some cases, they bend instead of breaking giving the illusion that they're up to the task but the grinding noise is an indicator not everything is well. Fix the ignition problem then have the starter repaired/replaced.
Clicks & Crickets	All - Lyc/Cont/Franklin	When we attempt to engage the starter, we hear a "click" but NOTHING happens	What is the voltage while cranking at the starter?	If the starter is not getting voltage, suspect the aircraft's firewall solenoid or switch. If the starter is getting >10 volts, suspect the starter's on board solenoid has failed. The solenoids on lightweight aircraft starters exposed to excessive vibration can wear 'pits' internally that do not allow the solenoid to pull-in (the starter doesn't engage and the motor doesn't get powered). Sky-Tec has made improvements to minimize the effect of this adverse vibration condition on our LS & PM model starters and will replace the starter mount with a vibration-resistant casting for significantly improved performance regardless of vibration levels. To return a starter to Sky-Tec, click here.
Clicks & Crickets with the smell of burned metal	All - Lyc/Cont/Franklin	When we attempt to engage the starter, we hear a "click" but NOTHING happens.	Smell your starter (hey, dogs do far worse). Does it smell burned? Does the battery pull down excessively when you energize the starter?	Sounds like a stuck firewall solenoid. See the Cessna Solenoid page for a detailed explanation. Your starter was most likely cooked by the failure of your firewall starter contactor (relay). A Sky-Tec starter cannot do this unto itself without an "upstream" failure of some kind (switch could also be suspect). Send that starter in for an overhaul.
Don't Let Go	Sky-Tec LS & PM models (Lycoming), CST2 models (Continental), & FST1 models (Franklin)	After start button is released, the starter stays engaged for nearly a second before releasing.	Does it stay engaged only for 1/2 to 2 seconds?	This is normal operation for a permanent magnet starter (Sky-Tec LS, PM, CST2, & FST1 models). Although power is removed by releasing the key/start button, a permanent magnet motor will actually provide power to itself as it winds-down and will keep the starter drive engaged for about a half-second until it loses sufficient RPM to fully disengage.
Hang 'em High	All	It appeared as though the starter drive gear stayed engaged for some length of time after the start button/key was released	Did you see smoke? Does the starter smelled like burnt metal?	A stuck firewall solenoid (starter contactor) can ruin your day AND your starter. Many older Cessna and Piper aircraft starter contactors are notorious for "welding shut" after years of use (often accelerated by the use of a high-current draw starter). Some of those older contactors (or relays as the case is) just cannot handle the increased starting current loads over a length of time. In some cases, the manufacturer even specified the wrong kind of starter solenoid in the application in the first place (see Cessna Firewall Solenoids). You may have few options besides overhauling or replacing your starter after replacing the culprit firewall solenoid.

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